A vehicle hill start assist control method
By controlling the motor output ramp assist torque through a dual closed-loop PI controller, the problem of the need for mechanical braking system participation in existing ramp start assist systems is solved, enabling vehicles to start smoothly on ramps, simplifying driver operation and improving safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUNAN CSR TIMES ELECTRIC VEHICLE
- Filing Date
- 2022-10-11
- Publication Date
- 2026-06-30
Smart Images
Figure CN117901657B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a vehicle hill start assist control method, specifically to the field of vehicle control technology. Background Technology
[0002] With the rapid development and increasing popularity of pure electric vehicles, people have higher and higher demands for their driving comfort and safety. Hill start is a complex situation that occurs frequently and has a high accident rate during vehicle operation. Improper operation may result in excessive power causing sudden acceleration, or insufficient power to balance the backward rolling force on the slope, thus requiring a high level of driving skill. Equipping vehicles with hill start assist systems can simplify driver operation and improve vehicle safety.
[0003] However, existing hill start assist systems usually require the participation of mechanical braking systems and complex operations by the driver, which makes it difficult for the vehicle to start smoothly on a slope, resulting in poor vehicle safety. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a vehicle hill start assist control method, which mainly solves the problem of vehicle rolling backward due to improper operation by the driver when starting on a hill, simplifies driver operation, and improves vehicle safety.
[0005] The content of this invention includes:
[0006] This invention provides a vehicle hill start assist control method, the method comprising:
[0007] S1. Collect the current status information of the vehicle;
[0008] S2. When the current status information meets the first preset condition, control the vehicle to enter the hill start assist mode;
[0009] S3. Obtain the actual rotational speed and actual rotational speed change rate of the vehicle, and calculate the ramp assist torque based on the actual rotational speed and actual rotational speed change rate;
[0010] S4. Control the vehicle to operate according to the ramp assist torque.
[0011] Optionally, S3 specifically includes:
[0012] S31. Obtain the actual rotational speed of the vehicle and calculate the difference between the target rotational speed and the actual rotational speed as the rotational speed difference.
[0013] S32. Input the speed difference value into the speed controller and output speed change rate compensation;
[0014] S33. Obtain the actual speed change rate of the vehicle, and calculate the difference between the speed change rate compensation and the actual speed change rate as the speed change rate difference;
[0015] S34. Input the difference in the rate of change of rotational speed into the rate of change of rotational speed controller, and output the ramp assist torque.
[0016] Optionally, both the speed controller and the speed change rate controller are PI controllers.
[0017] Optionally, the Kp and Ki parameters of the speed controller are obtained by looking up the corresponding motor speed change rate in a table.
[0018] Optionally, the current status information includes: vehicle key signal, gear signal, parking signal, accelerator pedal signal, brake pedal signal, and motor speed signal fed back by the motor controller.
[0019] Optionally, S2 specifically includes:
[0020] S21. Detect the vehicle key signal and determine whether the vehicle is powered on based on the key signal; if yes, proceed to S22; if no, proceed to S27.
[0021] S22. Detect the vehicle's gear position signal and determine whether the vehicle is in driving gear based on the gear position signal; if yes, execute S23; if no, execute S27.
[0022] S23. Detect the vehicle's parking signal and determine whether the vehicle's parking brake is invalid based on the parking signal; if yes, proceed to S24; if no, proceed to S27.
[0023] S24. Detect the vehicle's brake pedal signal and determine whether the vehicle's service brake is ineffective based on the brake pedal signal; if yes, proceed to S25; if no, proceed to S27.
[0024] S25. Detect the motor speed signal of the vehicle and determine whether the vehicle has a tendency to roll backward based on the motor speed signal; if yes, proceed to S26; if no, proceed to S27.
[0025] S26. Control the vehicle to enter hill start assist mode;
[0026] S27. Control the vehicle to exit the hill start assist mode.
[0027] Optionally, after S3, the method further includes:
[0028] S5. Obtain driving intention information, and when the driving intention information meets the second preset condition, control the vehicle to exit the hill start assist mode.
[0029] Optionally, the driving intention information includes accelerator pedal signal and requested torque information;
[0030] Specifically, S5 is:
[0031] When an accelerator pedal signal is detected, and the driver's requested torque is greater than the hill start assist torque, the vehicle is controlled to exit hill start assist mode.
[0032] Optionally, after S2, the method further includes:
[0033] S6. After a preset time has elapsed since entering the hill start assist mode, control the vehicle to exit the hill start assist mode.
[0034] Optionally, S4 specifically includes:
[0035] The ramp assist torque is sent to the vehicle's motor controller so that the motor controller controls the vehicle's motor to operate according to the ramp assist torque.
[0036] The beneficial effects of this invention are:
[0037] The vehicle hill start assist control method provided by this invention determines the timing of hill start assist intervention without adding sensors and actuators. It controls the motor to output hill start assist torque through a dual closed-loop PI controller, enabling the vehicle to quickly reach a balanced state on the slope and realize the hill start assist function within an acceptable backward roll distance. This achieves a smooth start on the slope, which simplifies driver operation and improves vehicle safety. Attached Figure Description
[0038] Appendix Figure 1 This is a flowchart of a vehicle hill start assist control method provided in an embodiment of the present invention;
[0039] Appendix Figure 2 This is a diagram illustrating the architecture of a vehicle hill start assist system provided in an embodiment of the present invention.
[0040] Appendix Figure 3 This is a decision diagram for the vehicle hill start assist mode provided in an embodiment of the present invention;
[0041] Appendix Figure 4 This is a block diagram of torque control for a vehicle hill start assist system provided in an embodiment of the present invention. Detailed Implementation
[0042] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments.
[0043] The power of a pure electric vehicle comes from a drive motor, which can output peak torque under low-speed and stall conditions, and its torque output is characterized by high precision and fast response. This invention proposes a method for hill start assist control of pure electric vehicles. It eliminates the need for a mechanical braking system and additional sensors, achieving a smooth hill start by controlling the motor's output drive torque to balance the backward slip force. The hill start assist system of this invention consists of a decision-making mechanism and an execution mechanism. The decision-making mechanism is the vehicle controller, and the execution mechanism is the motor and controller.
[0044] For details, see attached. Figure 1 To be continued Figure 4 As shown, the present invention provides a vehicle hill start assist control method, the method comprising:
[0045] S1. Collect the current status information of the vehicle.
[0046] The vehicle controller collects the vehicle's current status information, specifically: the vehicle's key signal, gear signal, parking signal, accelerator pedal signal, brake pedal signal, and motor speed signal fed back by the motor controller.
[0047] S2. When the current status information meets the first preset condition, control the vehicle to enter the hill start assist mode.
[0048] The vehicle controller makes mode decisions, determining when to enter and exit hill start assist mode, based on... Figure 2 As shown, it specifically includes:
[0049] S21. Detect the vehicle key signal and determine whether the vehicle is powered on based on the key signal; if yes, proceed to S22; otherwise, proceed to S27. Specifically, the vehicle controller detects the key signal to determine whether the vehicle is powered on. If the vehicle is powered on, proceed to the next step; otherwise, exit the hill start assist mode.
[0050] S22. Detect the vehicle's gear position signal and determine whether the vehicle is in drive gear based on the gear position signal; if yes, proceed to S23; otherwise, proceed to S27. Specifically, the vehicle controller detects the gear position signal to determine whether the vehicle is in drive gear. If the vehicle is in drive gear, proceed to the next step; otherwise, exit hill start assist mode.
[0051] S23. Detect the vehicle's parking signal and determine whether the vehicle's parking brake is invalid based on the parking signal; if yes, proceed to S24, otherwise proceed to S27; specifically, the vehicle controller detects the parking signal and determines whether the parking brake is valid. If the parking brake is invalid, proceed to the next process; otherwise, exit the hill start assist mode.
[0052] S24. Detect the vehicle's brake pedal signal and determine whether the vehicle's service brake is ineffective based on the brake pedal signal; if yes, proceed to S25, otherwise proceed to S27; specifically, the vehicle controller detects the brake pedal signal and determines whether the service brake is effective. If the service brake is ineffective, proceed to the next process; otherwise, exit the hill start assist mode.
[0053] S25. Detect the vehicle's motor speed signal and determine whether the vehicle has a tendency to roll backward based on the motor speed signal; if yes, execute S26, otherwise execute S27; specifically, the vehicle controller detects the motor speed signal, and when the motor speed is less than -3r / min, it is considered that the vehicle has a tendency to roll backward. If the vehicle has a tendency to roll backward, it enters the hill start assist mode; otherwise, it exits the hill start assist mode.
[0054] S26. Control the vehicle to enter hill start assist mode;
[0055] S27. Control the vehicle to exit hill start assist mode.
[0056] Furthermore, after S3, the method further includes:
[0057] S5. Obtain driving intention information, and when the driving intention information meets the second preset condition, control the vehicle to exit the hill start assist mode.
[0058] The driving intent information includes accelerator pedal signals and requested torque information;
[0059] Accordingly, S5 specifically means: when an accelerator pedal signal is detected and the driver's requested torque is greater than the hill start assist torque, the vehicle is controlled to exit the hill start assist mode.
[0060] Once hill start assist mode is activated, if the driver presses the accelerator pedal and requests torque greater than the hill start assist torque, indicating the driver's intention to leave the hill, then hill start assist mode will be deactivated.
[0061] Furthermore, after S2, the method further includes:
[0062] S6. After the preset time for entering hill start assist mode, control the vehicle to exit hill start assist mode.
[0063] The preset duration is a pre-set time length, which can be set by those skilled in the art according to actual conditions; this embodiment of the invention does not limit this. In practical applications, the preset duration can be set to 5 seconds.
[0064] Since the drive motor cannot be stalled for a long time, a timer starts after entering the hill start assist mode. If the time exceeds 5 seconds, the hill start assist mode will be exited.
[0065] S3. Obtain the vehicle's actual speed and actual speed change rate, and calculate the ramp assist torque based on the actual speed and actual speed change rate.
[0066] Specifically, it includes:
[0067] S31. Obtain the actual speed of the vehicle and calculate the difference between the target speed and the actual speed as the speed difference value.
[0068] S32. Input the speed difference into the speed controller and output the speed change rate compensation.
[0069] S33. Obtain the actual speed change rate of the vehicle and calculate the difference between the speed change rate compensation and the actual speed change rate as the speed change rate difference value.
[0070] S34. Input the speed change rate difference into the speed change rate controller and output the ramp assist torque.
[0071] Both the speed controller and the speed change rate controller are PI controllers. The Kp and Ki parameters of the speed controller are obtained by looking up the magnitude of the motor speed change rate when the vehicle rolls backward, thus reflecting the gradient and the vehicle's load.
[0072] Upon entering hill-start assist mode, the motor speed needs to be quickly and smoothly controlled to 0 r / min to maintain the drive motor in a stalled state, thereby preventing the vehicle from rolling backward. Existing technology uses an acceleration acquisition chip to obtain the vehicle's forward acceleration and calculates the road slope angle using the vehicle's longitudinal dynamics equations, estimating the initial motor torque based on the slope angle. This invention addresses sensorless scenarios by designing a dual closed-loop PI controller (proportional-integral controller) to adaptively adjust the hill-start assist torque, achieving both precise and rapid control. The framework is as follows: Figure 3 As shown.
[0073] The target speed is set to 0 r / min, and the difference between the target speed and the actual speed is used as the input to the speed PI controller. The closed-loop control output compensates for the rate of change of speed. The speed PI controller dynamically adjusts the rate of change of speed to follow the deviation between the actual and target speeds. Without driver intervention, the steeper the slope, the faster the vehicle rolls backward; the heavier the vehicle, the faster it rolls backward. Therefore, the Kp (proportional) and Ki (integral) parameters of the speed PI controller can be looked up using the motor speed change rate. Larger Kp and Ki parameters are used when the motor speed change rate is large to speed up the system response; smaller Kp and Ki parameters are used when the motor speed change rate is small to improve system response stability. For the dual-loop PI controller as a whole, the speed PI controller allows for adjustable speed at which the target speed approaches the actual speed.
[0074] The difference between the speed change rate compensation output by the speed PI controller and the actual speed change rate is used as the input to the speed change rate PI controller, which outputs the target torque, i.e., the ramp assist torque, in a closed loop. The speed change rate PI controller converts the current speed change rate deviation in the system into the target torque. Since the previous-stage speed PI controller has already considered the effects of gradient and vehicle weight on the system, the Kp and Ki parameters of the speed change rate PI controller can be constants.
[0075] S4. Control the vehicle to operate according to the ramp assist torque.
[0076] Specifically, the ramp assist torque is sent to the vehicle's motor controller so that the motor controller can control the vehicle's motor to operate according to the ramp assist torque.
[0077] The vehicle controller calculates the ramp assist torque and sends it to the motor controller. The motor and its controller receive and respond to the ramp assist torque sent by the vehicle controller, enabling the vehicle to quickly reach a balanced state on the ramp.
[0078] The vehicle hill start assist control method provided by this invention determines the timing of hill start assist intervention without adding sensors and actuators. It controls the motor to output hill start assist torque through a dual closed-loop PI controller, enabling the vehicle to quickly reach a balanced state on the slope and realize the hill start assist function within an acceptable backward roll distance. This achieves a smooth start on the slope, which simplifies driver operation and improves vehicle safety.
[0079] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A method for assisting vehicle hill start control, characterized in that, The method includes: S1. Collect the current status information of the vehicle; S2. When the current status information meets the first preset condition, control the vehicle to enter the hill start assist mode; S3. Obtain the actual rotational speed and actual rotational speed change rate of the vehicle, and calculate the ramp assist torque based on the actual rotational speed and actual rotational speed change rate; S3 specifically includes: S31. Obtain the actual rotational speed of the vehicle and calculate the difference between the target rotational speed and the actual rotational speed as the rotational speed difference. S32. Input the speed difference value into the speed controller and output speed change rate compensation; S33. Obtain the actual speed change rate of the vehicle, and calculate the difference between the speed change rate compensation and the actual speed change rate as the speed change rate difference; S34. Input the speed change rate difference into the speed change rate controller and output the ramp assist torque; Both the speed controller and the speed change rate controller are PI controllers. The Kp and Ki parameters of the speed controller are obtained by looking up the magnitude of the motor speed change rate when the vehicle rolls backward. The Kp and Ki parameters of the speed change rate controller are constants. S4. Control the vehicle to operate according to the ramp assist torque.
2. The method as described in claim 1, characterized in that, The current status information includes: vehicle key signal, gear signal, parking signal, accelerator pedal signal, brake pedal signal, and motor speed signal fed back by the motor controller.
3. The method as described in claim 2, characterized in that, S2 specifically includes: S21. Detect the vehicle key signal and determine whether the vehicle is powered on based on the key signal; if yes, proceed to S22; if no, proceed to S27. S22. Detect the vehicle's gear position signal and determine whether the vehicle is in driving gear based on the gear position signal; if yes, execute S23; if no, execute S27. S23. Detect the vehicle's parking signal and determine whether the vehicle's parking brake is invalid based on the parking signal; if yes, proceed to S24; if no, proceed to S27. S24. Detect the vehicle's brake pedal signal and determine whether the vehicle's service brake is ineffective based on the brake pedal signal; if yes, proceed to S25; if no, proceed to S27. S25. Detect the motor speed signal of the vehicle and determine whether the vehicle has a tendency to roll backward based on the motor speed signal; if yes, proceed to S26; if no, proceed to S27. S26. Control the vehicle to enter hill start assist mode; S27. Control the vehicle to exit the hill start assist mode.
4. The method as described in claim 3, characterized in that, Following S3, the method further includes: S5. Obtain driving intention information, and when the driving intention information meets the second preset condition, control the vehicle to exit the hill start assist mode.
5. The method as described in claim 4, characterized in that, The driving intent information includes accelerator pedal signals and requested torque information; Specifically, S5 is: When an accelerator pedal signal is detected, and the driver's requested torque is greater than the hill start assist torque, the vehicle is controlled to exit hill start assist mode.
6. The method as described in claim 3 or 4, characterized in that, Following S2, the method further includes: S6. After a preset time has elapsed since entering the hill start assist mode, control the vehicle to exit the hill start assist mode.
7. The method as described in claim 1, characterized in that, Specifically, S4 is: The ramp assist torque is sent to the vehicle's motor controller so that the motor controller controls the vehicle's motor to operate according to the ramp assist torque.